• N SIVANANTHAM

      Articles written in Bulletin of Materials Science

    • Effect of heat treatment on the optical properties of layered muscovite single crystal sheets

      M KIRUBANITHY N SIVANANTHAM N GOPALAKRISHNAN K BALAMURUGAN

      More Details Abstract Fulltext PDF

      Naturally, thin sheets of layered, dioctahedral muscovite single crystals are transparent to visible light. Upon heat treatments performed up to 900$^{\circ}$C, the single crystal sheets of thickness $\sim$200 $\mu$m exhibited changes in its optical transparent character. The muscovite sheets exhibited either translucent or nontransparent, dark-brown, gold or copper like luster, varying optical band gap (from $\sim$3.7 to 2.7 eV) and photoluminescence (PL) properties, which depend on the temperature of the heat treatment. A comprehensive investigation has been made using X-ray diffraction, thermal analyses, energy dispersive X-ray and Raman spectroscopies to understand how/why the optical properties of the muscovite sheets changed up on heat treatments. Besides, no phase changes were found in the layered, lamellar crystal structure, evidences for the known dehydroxylation of muscovite were clearly seen from the thermal analyses data. Further, the Raman spectrum of the muscovite sheet heat treated at 900$^{\circ}$C showed no evidence for the presence of hydroxyl group (OH$^−$), which confirmed the completion of the dehydroxylation. The dihydroxylation-induced changes in the structural-elements (for example, Al-(O,OH)$_6$ partly or fully changing to Al-O$_5$/O$_6$ and its effects on the lattice constants, and also the defect levels introduced by the heat treatments are responsible for the changes in the optical transparency, colour of appearance, band gap and PL of the muscovite natural single crystal sheets.

  • Bulletin of Materials Science | News

    • Dr Shanti Swarup Bhatnagar for Science and Technology

      Posted on October 12, 2020

      Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.